Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$131.52	8.615%	$142.8504	$142.85	$142.85	$142.90
Purchase #2	$112.48	13.633%	$127.8144	$127.81	$127.80	$127.80
Purchase #3	$59.36	5.212%	$62.4538	$62.45	$62.45	$62.50
Purchase #4	$152.53	6.425%	$162.3301	$162.33	$162.35	$162.30
Purchase #5	$183.56	8.243%	$198.6909	$198.69	$198.70	$198.70
Purchase #6	$167.90	7.550%	$180.5765	$180.58	$180.60	$180.60
Purchase #7	$71.93	8.150%	$77.7923	$77.79	$77.80	$77.80
7 purchase totals =	$879.28		$952.5084	$952.50	$952.55	$952.60